Rho1 Eridani

For other star systems with this Bayer designation, see Rho Eridani.

ρ^1 Eridani

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Eridanus
Right ascension	03^h 01^m 10.02608^s[1]
Declination	−07° 39′ 46.8232″[1]
Apparent magnitude (V)	5.75[2]
Characteristics
Spectral type	K0 III[3]
U−B color index	+0.86[2]
B−V color index	+1.04[2]
Astrometry
Radial velocity (Rv)	13.68±0.33[4] km/s
Proper motion (μ)	RA: +101.02[1] mas/yr Dec.: −69.97[1] mas/yr
Parallax (π)	10.07 ± 0.51 mas[1]
Distance	320 ± 20 ly (99 ± 5 pc)
Absolute magnitude (MV)	0.899[5]
Details
Mass	2.05[5] M☉
Radius	10[4] R☉
Luminosity	46.9[4] L☉
Surface gravity (log g)	2.7[4] cgs
Temperature	4,710[4] K
Metallicity [Fe/H]	0.09[5] dex
Rotational velocity (v sin i)	2.4[4] km/s
Other designations
ρ^1 Eridani, ρ^1 Eri, 8 Eridani, BD−08°562, HD 18784, HIP 14060, HR 907, SAO 130243.[6]
Database references
SIMBAD	data

Rho¹ Eridani (Rho¹ Eri, ρ¹ Eri), is a star located in the constellation Eridanus. It forms an asterism with the stars Rho² and Rho³ Eridani, south of Cetus, in the upper north east portion of Eridanus. The star has an apparent visual magnitude of 5.75,^[2] which indicates it is faintly visible to the naked eye on a clear, dark night. Based upon parallax measurements made with the Hipparcos satellite, this star is roughly 320 light years away from the Sun. Judging from changes to its proper motion, there is a chance that this is an astrometric binary.^[7]

This is an evolved K-type giant star with a stellar classification of K0 III.^[3] It is a red clump giant on the horizontal branch of the Hertzsprung–Russell diagram, indicating that is it now generating energy through the thermonuclear fusion of helium at its core.^[5] The star has more than twice the mass of the Sun and has expanded to 10 times the Sun's radius. As such, it is radiating nearly 47 times the solar luminosity from its outer atmosphere at an effective temperature of 4,710 K.^[4]

References

1. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
2. Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.
3. Houk, N.; Swift, C. (1999), "Michigan catalogue of two-dimensional spectral types for the HD Stars", Michigan Spectral Survey, 5, Bibcode:1999MSS...C05....0H.
4. Massarotti, Alessandro; et al. (January 2008), "Rotational and radial velocities for a sample of 761 HIPPARCOS giants and the role of binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209.
5. Zhao, G.; et al. (2001). "High-Resolution Spectroscopic Observations of Hipparcos Red Clump Giants: Metallicity and Mass Determinations". The Astrophysical Journal. 551 (1): L85. Bibcode:2001ApJ...551L..85Z. doi:10.1086/319832. S2CID 119700315.
6. "* rho01 Eri". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2016-10-12.
7. Fuhrmann, K.; Chini, R. (August 2015), "Multiplicity among F-type Stars. II", The Astrophysical Journal, 809 (1): 19, Bibcode:2015ApJ...809..107F, doi:10.1088/0004-637X/809/1/107, 107.